using System;

using System.Collections;

using System.Configuration;

using System.Data;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using YTLib.Basic;

using YTLib.YTDBC;

using System.IO;

using System.Threading;

namespace siteadmin.admin

{

    public partial class downfile : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

                 string strSQL = "";

                YTNDBObject dbo = new YTNDBObject();

                dbo.DataName = "Main";

            Page.EnableViewState = false;

            if(!IsPostBack)

            {

                string sid=Request["id"];

                if(!YTLib.publicOP.IsNumString(sid)||sid==null)

                    sid="0";

                strSQL = "select * from FileSource where ID=@ID";

                dbo.PrepareCommand(strSQL);

                dbo.SetCmdIntValue("@ID",int.Parse(sid));

                DataTable dt=dbo.QueryData().Tables[0];

                string sourceName = (string)dt.Rows[0]["FilePath"];

                sourceName.Trim();//消除空格

                string filesnames = sourceName.Substring(7, sourceName.Length - 8);

                int index= sourceName.LastIndexOf(".");

                string extend = sourceName.Substring(index+1);//扩展名

                string fullPath = "~/uploaded/" + sourceName;

                fullPath = Server.MapPath(fullPath);

                //读出该资源的下载次数

                int downloadtimes = 0;

                downloadtimes = int.Parse(dt.Rows[0]["downloadCounts"].ToString());

 

                         Page.Response.Clear();

                         bool success = ResponseFile(Page.Request, Page.Response, filesnames, fullPath, 1024000);

                if (!success) Response.Write("<script language=\"javascript\">alert(\"Download file error\");window.location.href=\"../Download.aspx\"</script>");

                else

                {

                    //记录下载次数

                    downloadtimes++;

                   string  sqlStr = "update FileSource set downloadCounts=" + downloadtimes + " where ID=@IID";

                   dbo.PrepareCommand(sqlStr);

                    dbo.SetCmdIntValue("@IID",int.Parse(sid));

                    dbo.ExecuteNoQuery();

                }

               Response.Write("<script language=\"javascript\">window.location.href=\"../Download.aspx\"</script>");

            }

        }

    public static bool ResponseFile(HttpRequest _Request, HttpResponse _Response, string _fileName, string _fullPath, long _speed)

    {

        try

        {

            FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);

            BinaryReader br = new BinaryReader(myFile);

            try

            {

                _Response.AddHeader("Accept-Ranges", "bytes");

                _Response.Buffer = false;//不缓冲

                long fileLength = myFile.Length;

                long startBytes = 0;

                double pack = 10240;

                //10K bytes

                int sleep = 200;

                //每秒5次 即5*10K bytes每秒 int sleep = (int)Math.Floor(1000 * pack / _speed) + 1;

                if (_Request.Headers["Range"] != null)

                {

                    _Response.StatusCode = 206;

                    string[] range = _Request.Headers["Range"].Split(new char[] { '=', '-' });

                    startBytes = Convert.ToInt64(range[1]);

                }

                _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());

                if (startBytes != 0)

                {

                    //Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength-1, fileLength));

                }

                _Response.AddHeader("Connection", "Keep-Alive");

                _Response.ContentType = "application/octet-stream";

                _Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(_fileName, System.Text.Encoding.UTF8));

                br.BaseStream.Seek(startBytes, SeekOrigin.Begin);

                int maxCount = (int)Math.Floor((fileLength - startBytes) / pack) + 1;

                for (int i = 0; i < maxCount; i++)

                {

                    if (_Response.IsClientConnected)

                    {

                        _Response.BinaryWrite(br.ReadBytes(int.Parse(pack.ToString())));

                        Thread.Sleep(sleep);

                    }

                    else

                    {

                        i = maxCount;

                    }

                }

            }

            catch

            {

                return false;

            }

            finally

            {

                br.Close();

                myFile.Close();

            }

        }

        catch

        {

            return false;

        }

        return true;

    }

        }

    }